Cardiovascular diseases (CVD) are the leading causes of death and disability in the US. Obesity and its behavioral components, lack of physical activity and poor diet, are major determinants of CVD. Prevention of obesity and its CVD sequelae are clinical and public health priorities. Yet the origins of obesity remain poorly understood and many potential solutions to the problem are understudied. To address these challenges, four years ago we established the Obesity Prevention Program at the Department of Ambulatory Care and Prevention, a joint department of Harvard Medical School and Harvard Pilgrim Health Care situated at the fulcrum of academia, medical delivery systems, and public health. The mission of this interdisciplinary research Program is to lessen the burden of obesity-related disorders by conducting epidemiologic, intervention, and health services research studies within defined populations of children and adults. After a competitive international search, we successfully recruited Dr. Jason Block, a general internist just finishing a highly productive fellowship in health services and health policy, to join our full-time faculty as of June 2009. A base of solid financial support as he joins the ranks of our junior faculty will allow him to take off as a Newly Independent Investigator. The goal of the proposed NHLBI PSO Core Center is to support Dr. Block's salary and startup research activities along with a pilot grants program. so that the Obesity Prevention Program can expand and intensify its research in health services, health policy, and comparative effectiveness research The Program's location within Harvard's Department of Ambulatory Care and Prevention provides unparalleled resources for conducting this type of research. Because of a precipitous drop in endowment funds, Harvard Medical School will eliminate its financial support to the department that we intended to use for Dr. Block's initial salary and startup research activities. While the department will use other resources to honor its commitment to Dr. Block's salary, it does not have committed resources to pay for his initial research activities. Having startup support for staff, equipment, and supplies and the ability to obtain pilot project funding from the proposed Core Center will be critical to Dr. Block's ability to take advantage of time-limited research opportunities. In addition, because the proposed Core Center will support Dr. Block's salary during his first two years on the OPP faculty, it will free the department to guarantee his salary for at least two more years. Thus the proposed NHLBI PSO Core Center grant will provide a crucial boost to Newly Independent Investigator Dr. Block, and will benefit not only his own career but also the Obesity Prevention Program as a whole. Obesity has grown unchecked in recent years and has thus far eluded easy answers despite its powerful adverse effects on health. New solutions may very well come from research in health services, health policy, and comparative effectiveness. By funding a Newly Independent Investigator, startup research activities, and a pilot grants program, this NHLBI PSO Core Center grant comes at just the right time to support the Obesity Prevention Program at Harvard's Department of Ambulatory Care and Prevention to expand and intensify its research in these increasingly important areas.